Breaking Balls

Impact of Outfield Defense

the archives are now free.

All Baseball Prospectus Premium and Fantasy articles more than a year old are now free as a thank you to the entire Internet for making our work possible.

Not a subscriber? Get exclusive content like this delivered hot to your inbox every weekday. Click here for more information on Baseball Prospectus subscriptions or use the buttons to the right to subscribe and get instant access to the best baseball content on the web.

Looking at outfield defenses, I found that the difference between the best and the worst outfield defenses worked out to around 150 hits, given an average pitching staff and equal chances. These are the fly balls that skip past Carl Everett and are devoured by Darin Erstad.

For purposes of this column, figure 33% of those go for doubles. Generally, doubles are about 20% of all hits, including ground-ball hits, so if anything, that's a little conservative. And also for purposes of this example, we're playing in an average park with an average pitching staff backed up by an average infield. The average AL team last year hit .264/.327/.424, while the average NL team hit .259/.327/.410.

Let's say that you're in the NL, with an average outfield, and you replace those players with all-stick immobile outfielders and punt outfield defense--we'll call these guys the Kahrls. What happens to your pitchers?

Seventy-five outs are turned into hits, hits that are followed by another plate appearance, for starters. This may seem odd at first, but the batter who would have gotten out is now on base, and replaced by the next guy in the order, resulting in another plate appearance. So first, there's the 75 hits, 23 of which are doubles. And for those 75 plate appearances you're giving away, figure that they'll work out at a league-average rate (which is generous, since you've just crippled your outfield). That's going to be 19 hits, 4 doubles, 2 home runs, and 7 walks. Combined, the pitching line is going to go from .259/.327/.410 line to an uglier .273/.340/.428. You're upgrading every Eric Karros to Tino Martinez, through all nine spots in every lineup, every day.

Ah, but it doesn't stop there--of the extra 75 guys the pitchers now have to face, the pitchers didn't get them all out, and have to keep on pitching until they get those outs (well, not entirely, since they could be losing now to the home team in the bottom of the ninth, or extra innings, but bear with me). So I ran some simple numbers on what happened in getting those 75 outs, and in the end, it's 113 more plate appearances, 29 hits, 5 extra doubles, 3 HR, and 10 walks.

What if, by contrast, you replaced your average outfield with the speediest, most hyperactive kids you can find in the minor leagues--we'll call them the Jonahs--juiced them up on caffeine, and let them loose in the outfield to catch all the balls they can? The same thing, in reverse: You immediately turn 75 hits into outs, and then go through and remove the guys who came up because of those 75 hits, and then...same deal as before in reverse, pretty much. Run the same formulas...here's what I figured the pitching staffs gave up:

The effects of turning hits into outs are much larger than they would initially seem. The outfield of Jonahs could take a team from an average unit giving up 700 runs to one that could get under 650 without much trouble, a swing of five games. At the opposite end, a set of immobile Kahrls is going to have to hit the ball hard and often, because they're going to be giving up another 50 runs just as easily, and probably more than that.

Another interesting way to look at this, as suggested by some readers, is to think of the defenders as being credited offensively by their defensive play. Take the Jonahs, above--they're saving at least 50 runs with their fielding. As a unit, they could hit .244/.313/.390 and credited for their run prevention, they're right back in the middle of the pack at .260/.330/.400 or thereabouts. Even hitting like their now-frustrated opponents, overall they would be an average outfield unit (particularly beloved by their pitchers, I'd imagine).

Now all of this is fun, but it's not like I ran particularly sophisticated analysis that looked at the distribution of play-by-play situations or baserunning. In particular, the marginal effect of downgrading the defense means that the hypothetical batters we add or subtract will be more or less effective, rather than league-average, which would make the spread even larger. Still, there are two things here that are immediately obvious. First, that there are indeed many games to be won or lost through outfield defense, and second, it may offer us insight into where surprise teams can come from. You can gain five wins in run prevention by upgrading your outfield defense from average to great, converting singles, doubles, and triples into outs and lesser hits.